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authorJeff Layton <jlayton@redhat.com>2011-04-02 15:34:30 +0400
committerSteve French <sfrench@us.ibm.com>2011-04-12 04:58:28 +0400
commit157c249114508aa71daa308a426e15d81a4eed00 (patch)
tree401c8aefddc465a2ff780d8982ddafd62d36506c /fs/cifs
parent581ade4d1c025eb10421eda0d0c0a2f04447d7c5 (diff)
downloadlinux-157c249114508aa71daa308a426e15d81a4eed00.tar.xz
cifs: wrap received signature check in srv_mutex
While testing my patchset to fix asynchronous writes, I hit a bunch of signature problems when testing with signing on. The problem seems to be that signature checks on receive can be running at the same time as a process that is sending, or even that multiple receives can be checking signatures at the same time, clobbering the same data structures. While we're at it, clean up the comments over cifs_calculate_signature and add a note that the srv_mutex should be held when calling this function. This patch seems to fix the problems for me, but I'm not clear on whether it's the best approach. If it is, then this should probably go to stable too. Cc: stable@kernel.org Cc: Shirish Pargaonkar <shirishpargaonkar@gmail.com> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
Diffstat (limited to 'fs/cifs')
-rw-r--r--fs/cifs/cifsencrypt.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index e307a286a1e5..d1a016be73ba 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -30,12 +30,13 @@
#include <linux/ctype.h>
#include <linux/random.h>
-/* Calculate and return the CIFS signature based on the mac key and SMB PDU */
-/* the 16 byte signature must be allocated by the caller */
-/* Note we only use the 1st eight bytes */
-/* Note that the smb header signature field on input contains the
- sequence number before this function is called */
-
+/*
+ * Calculate and return the CIFS signature based on the mac key and SMB PDU.
+ * The 16 byte signature must be allocated by the caller. Note we only use the
+ * 1st eight bytes and that the smb header signature field on input contains
+ * the sequence number before this function is called. Also, this function
+ * should be called with the server->srv_mutex held.
+ */
static int cifs_calculate_signature(const struct smb_hdr *cifs_pdu,
struct TCP_Server_Info *server, char *signature)
{
@@ -209,8 +210,10 @@ int cifs_verify_signature(struct smb_hdr *cifs_pdu,
cpu_to_le32(expected_sequence_number);
cifs_pdu->Signature.Sequence.Reserved = 0;
+ mutex_lock(&server->srv_mutex);
rc = cifs_calculate_signature(cifs_pdu, server,
what_we_think_sig_should_be);
+ mutex_unlock(&server->srv_mutex);
if (rc)
return rc;